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08-bootstrapping-kubernetes-controllers.md

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Bootstrapping the Kubernetes Control Plane

In this lab you will bootstrap the Kubernetes control plane across three VM instances and configure it for high availability. You will also create a load balancer that exposes the Kubernetes API Servers to remote clients. The following components will be installed on each node: Kubernetes API Server, Scheduler, and Controller Manager.

Prerequisites

The commands in this lab must be run on each controller instance: controller-0, controller-1, and controller-2. Login to each controller instance using the ssh command. Example:

ssh root@controller-0

Running commands in parallel with tmux

tmux can be used to run commands on multiple compute instances at the same time. See the Running commands in parallel with tmux section in the Prerequisites lab.

Provision the Kubernetes Control Plane

Create the Kubernetes configuration directory:

sudo mkdir -p /etc/kubernetes/config

Download and Install the Kubernetes Controller Binaries

Download the official Kubernetes release binaries:

wget -q --show-progress --https-only --timestamping \
  "https://storage.googleapis.com/kubernetes-release/release/v1.29.1/bin/linux/amd64/kube-apiserver" \
  "https://storage.googleapis.com/kubernetes-release/release/v1.29.1/bin/linux/amd64/kube-controller-manager" \
  "https://storage.googleapis.com/kubernetes-release/release/v1.29.1/bin/linux/amd64/kube-scheduler" \
  "https://storage.googleapis.com/kubernetes-release/release/v1.29.1/bin/linux/amd64/kubectl"

Install the Kubernetes binaries:

chmod +x kube-apiserver kube-controller-manager kube-scheduler kubectl
sudo mv kube-apiserver kube-controller-manager kube-scheduler kubectl /usr/local/bin/

Configure the Kubernetes API Server

sudo mkdir -p /var/lib/kubernetes/

sudo mv ca.pem ca-key.pem kubernetes-key.pem kubernetes.pem \
  service-account-key.pem service-account.pem \
  encryption-config.yaml /var/lib/kubernetes/

The instance internal IP address will be used to advertise the API Server to members of the cluster. Define the INTERNAL_IP (replace MY_NODE_INTERNAL_IP by the value):

INTERNAL_IP=MY_NODE_INTERNAL_IP

Example for controller-0 : 192.168.8.10

Create the kube-apiserver.service systemd unit file:

KUBERNETES_PUBLIC_ADDRESS=MY_PUBLIC_IP_ADDRESS

cat <<EOF | sudo tee /etc/systemd/system/kube-apiserver.service
[Unit]
Description=Kubernetes API Server
Documentation=https://github.com/kubernetes/kubernetes

[Service]
ExecStart=/usr/local/bin/kube-apiserver \\
  --advertise-address=${INTERNAL_IP} \\
  --allow-privileged=true \\
  --apiserver-count=3 \\
  --audit-log-maxage=30 \\
  --audit-log-maxbackup=3 \\
  --audit-log-maxsize=100 \\
  --audit-log-path=/var/log/audit.log \\
  --authorization-mode=Node,RBAC \\
  --bind-address=0.0.0.0 \\
  --client-ca-file=/var/lib/kubernetes/ca.pem \\
  --enable-admission-plugins=NamespaceLifecycle,NodeRestriction,LimitRanger,ServiceAccount,DefaultStorageClass,ResourceQuota \\
  --etcd-cafile=/var/lib/kubernetes/ca.pem \\
  --etcd-certfile=/var/lib/kubernetes/kubernetes.pem \\
  --etcd-keyfile=/var/lib/kubernetes/kubernetes-key.pem \\
  --etcd-servers=https://192.168.8.10:2379,https://192.168.8.11:2379,https://192.168.8.12:2379 \\
  --event-ttl=1h \\
  --encryption-provider-config=/var/lib/kubernetes/encryption-config.yaml \\
  --kubelet-certificate-authority=/var/lib/kubernetes/ca.pem \\
  --kubelet-client-certificate=/var/lib/kubernetes/kubernetes.pem \\
  --kubelet-client-key=/var/lib/kubernetes/kubernetes-key.pem \\
  --runtime-config=api/all=true \\
  --service-account-key-file=/var/lib/kubernetes/service-account.pem \\
  --service-account-signing-key-file=/var/lib/kubernetes/service-account-key.pem \\
  --service-account-issuer=https://${KUBERNETES_PUBLIC_ADDRESS}:6443 \\
  --service-cluster-ip-range=10.32.0.0/24 \\
  --service-node-port-range=30000-32767 \\
  --tls-cert-file=/var/lib/kubernetes/kubernetes.pem \\
  --tls-private-key-file=/var/lib/kubernetes/kubernetes-key.pem \\
  --v=2
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target
EOF

Configure the Kubernetes Controller Manager

Move the kube-controller-manager kubeconfig into place:

sudo mv kube-controller-manager.kubeconfig /var/lib/kubernetes/

Create the kube-controller-manager.service systemd unit file:

cat <<EOF | sudo tee /etc/systemd/system/kube-controller-manager.service
[Unit]
Description=Kubernetes Controller Manager
Documentation=https://github.com/kubernetes/kubernetes

[Service]
ExecStart=/usr/local/bin/kube-controller-manager \\
  --bind-address=0.0.0.0 \\
  --cluster-cidr=10.200.0.0/16 \\
  --cluster-name=kubernetes \\
  --cluster-signing-cert-file=/var/lib/kubernetes/ca.pem \\
  --cluster-signing-key-file=/var/lib/kubernetes/ca-key.pem \\
  --kubeconfig=/var/lib/kubernetes/kube-controller-manager.kubeconfig \\
  --leader-elect=true \\
  --root-ca-file=/var/lib/kubernetes/ca.pem \\
  --service-account-private-key-file=/var/lib/kubernetes/service-account-key.pem \\
  --service-cluster-ip-range=10.32.0.0/24 \\
  --use-service-account-credentials=true \\
  --v=2
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target
EOF

Configure the Kubernetes Scheduler

Move the kube-scheduler kubeconfig into place:

sudo mv kube-scheduler.kubeconfig /var/lib/kubernetes/

Create the kube-scheduler.yaml configuration file:

cat <<EOF | sudo tee /etc/kubernetes/config/kube-scheduler.yaml
apiVersion: kubescheduler.config.k8s.io/v1
kind: KubeSchedulerConfiguration
clientConnection:
  kubeconfig: "/var/lib/kubernetes/kube-scheduler.kubeconfig"
leaderElection:
  leaderElect: true
EOF

Create the kube-scheduler.service systemd unit file:

cat <<EOF | sudo tee /etc/systemd/system/kube-scheduler.service
[Unit]
Description=Kubernetes Scheduler
Documentation=https://github.com/kubernetes/kubernetes

[Service]
ExecStart=/usr/local/bin/kube-scheduler \\
  --config=/etc/kubernetes/config/kube-scheduler.yaml \\
  --v=2
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target
EOF

Start the Controller Services

sudo systemctl daemon-reload
sudo systemctl enable kube-apiserver kube-controller-manager kube-scheduler
sudo systemctl start kube-apiserver kube-controller-manager kube-scheduler

Allow up to 10 seconds for the Kubernetes API Server to fully initialize.

Verification

kubectl cluster-info --kubeconfig admin.kubeconfig
Kubernetes control plane is running at https://127.0.0.1:6443

Test the HTTPS health check :

curl -kH "Host: kubernetes.default.svc.cluster.local" -i https://127.0.0.1:6443/healthz
HTTP/2 200
content-type: text/plain; charset=utf-8
x-content-type-options: nosniff
content-length: 2
date: Wed, 24 Jun 2020 12:24:52 GMT

ok

Remember to run the above commands on each controller node: controller-0, controller-1, and controller-2.

RBAC for Kubelet Authorization

In this section you will configure RBAC permissions to allow the Kubernetes API Server to access the Kubelet API on each worker node. Access to the Kubelet API is required for retrieving metrics, logs, and executing commands in pods.

This tutorial sets the Kubelet --authorization-mode flag to Webhook. Webhook mode uses the SubjectAccessReview API to determine authorization.

The commands in this section will effect the entire cluster and only need to be run once from one of the controller nodes.

ssh root@controller-0

Create the system:kube-apiserver-to-kubelet ClusterRole with permissions to access the Kubelet API and perform most common tasks associated with managing pods:

cat <<EOF | kubectl apply --kubeconfig admin.kubeconfig -f -
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  annotations:
    rbac.authorization.kubernetes.io/autoupdate: "true"
  labels:
    kubernetes.io/bootstrapping: rbac-defaults
  name: system:kube-apiserver-to-kubelet
rules:
  - apiGroups:
      - ""
    resources:
      - nodes/proxy
      - nodes/stats
      - nodes/log
      - nodes/spec
      - nodes/metrics
    verbs:
      - "*"
EOF

The Kubernetes API Server authenticates to the Kubelet as the kubernetes user using the client certificate as defined by the --kubelet-client-certificate flag.

Bind the system:kube-apiserver-to-kubelet ClusterRole to the kubernetes user:

cat <<EOF | kubectl apply --kubeconfig admin.kubeconfig -f -
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: system:kube-apiserver
  namespace: ""
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: system:kube-apiserver-to-kubelet
subjects:
  - apiGroup: rbac.authorization.k8s.io
    kind: User
    name: kubernetes
EOF

The Kubernetes Frontend Load Balancer

In this section you will provision an Nginx load balancer to front the Kubernetes API Servers. The load balancer will listen on the private and the public IP address (on the gateway-01 VM).

Provision an Nginx Load Balancer

Install the Nginx Load Balancer and stream library:

sudo apt-get update
sudo apt-get install -y nginx libnginx-mod-stream

As root user, Create the Nginx load balancer network configuration:

cat <<EOF >> /etc/nginx/nginx.conf
stream {
    upstream controller_backend {
        server 192.168.8.10:6443;
        server 192.168.8.11:6443;
        server 192.168.8.12:6443;
    }
    server {
        listen     6443;
        proxy_pass controller_backend;
        # health_check; # Only Nginx commercial subscription can use this directive...
    }
}
EOF

Restart the service:

sudo systemctl restart nginx

Enable the service:

sudo systemctl enable nginx

Load Balancer Verification

Define the static public IP address (replace MY_PUBLIC_IP_ADDRESS with your public IP address on the gateway-01 VM):

KUBERNETES_PUBLIC_ADDRESS=MY_PUBLIC_IP_ADDRESS

Make a HTTP request for the Kubernetes version info:

curl --cacert ca.pem https://${KUBERNETES_PUBLIC_ADDRESS}:6443/version

output

{
  "major": "1",
  "minor": "29",
  "gitVersion": "v1.29.1",
  "gitCommit": "bc401b91f2782410b3fb3f9acf43a995c4de90d2",
  "gitTreeState": "clean",
  "buildDate": "2024-01-17T15:41:12Z",
  "goVersion": "go1.21.6",
  "compiler": "gc",
  "platform": "linux/amd64"
}

Next: Bootstrapping the Kubernetes Worker Nodes